walk_category_dropdown_tree()

function walk_category_dropdown_tree() {
	$args = func_get_args();
	// the user's options are the third parameter
	if ( empty( $args[2]['walker'] ) || ! ( $args[2]['walker'] instanceof Walker ) ) {
		$walker = new Walker_CategoryDropdown;
	} else {
		$walker = $args[2]['walker'];
	}
	return call_user_func_array( array( $walker, 'walk' ), $args );
}